Quote from the article:

"America's school kids have historically scored low on international assessment tests compared to other countries, which is often blamed on the diversity of the population and the high number of immigrants."

America's diversity is a creation myth. Outside of New York, it isn't very diverse at all, and compared to Western Europe it doesn't have a very high number of immigrants.

Or does the American definition of 'diversity' only refer to the number of black people? In that case, blaming their numbers for lower test scores is kind of ... racist, isn't it?